Observational evidence for cylindrically oriented zonal flows on Jupiter

The atmospheric dynamics of Jupiter are dominated by strong zonal winds engulfing the planet. Since the first gravity measurements of Juno at Jupiter, the low-degree gravity harmonics (J 3 -J 10 ) have been used to determine the depth and structure of the zonal winds observed at the cloud level, limiting the inference on the deep flows to the wide latitudinal structure of these harmonics. Here, using constraints on the dynamical contribution to gravity at high latitude, we present the gravity harmonics up to J 40. We find an excellent correlation between these measurements and the gravity harmonics resulting from the observed cloud-level winds extending inward cylindrically to depths of ∼ 10 5 bar (3000 km). These measurements provide direct evidence that the flows penetrate inward along the direction of the spin axis, confirming the cylindrical nature of the flow, which has been postulated theoretically since the 1970s. Furthermore, this detailed new gravity spectrum allows to quantify the contribution of the various jets to the gravity signal, showing the dominance of the strong flows around latitude 20 • in both hemispheres.